Investigation of the NMR enhancement factor in CuMn spin glasses

The NMR enhancement factor of a frozenCuMn spin glass has been measured at a temperatureT?T _g /5. The measurements were performed as function of static magnetic fields of different directions. A two component model of a spin glass has been outlined. One component being a “system of single spins” and the other one being a “subsystem of clusters”. Both components were attributed to different kinds of interaction being RKKY and dipole interaction respectively. The effective anisotropy field of the single spin system consists of two unidirectional contributionsH _a ^s andH _a ^c , which have been measured for different conditions. A second anisotropy fieldH _d binds the cluster system to the system of single spins. All anisotropy fields depend on the annealing temperature of the alloys.     

Untersuchungen über den Phytolgehalt von Pflanzen

Zusammenfassung Es wurde festgestellt, daß der Phytolgehalt von Blättern der Roßkastanie (Aesculus hippocastanum) im Laufe der Vegetationsperiode von praktisch Null in den Knospen mit der Ausbildung der Blätter rasch zum Maximalwert ansteigt. Es sind keine Anhaltspunkte dafür gegeben, daß wesentliche Phytolmengen außer den im Chlorophyll gebundenen in den Knospen oder grünen Blättern vorhanden sind. Dagegen bleibt bei der herbstlichen Laubverfärbung der Phytolgehalt noch erhalten und nimmt erst mit der Verrottung der abgefallenen Blätter ab.Blätter und Stengel von Feuerbohnen (Phaseolus multiflorus), die in Dunkelheit gezogen wurden und praktisch chlorophyllfrei waren, enthielten auch kein Phytol.     

Synthesis of a phosphine-modified cyclodextrin and its rhodium complex

A bidentate ligand consisting of a 2-(diphenylphosphinoethyl)-thio moiety was attached to β-cyclodextrin at the 6-position. The corresponding norbornadiene Rh(I) complex in the form of the BF₄⁻ salt was prepared.     

Extraction of gallium(III) and aluminium(III) with O,O-dialkyldithiophosphoric acids

The extraction of Ga³⁺ and Al³⁺ with the liquid cation-exchangers di-n-butyldithiophosphoric acid (DBTPA) and di-(2-ethylhexyl)dithiophosphoric acid (DETPA) in kerosene, in the presence and absence of alcohols and tri-n-butyl phosphate (TBP) has been studied. Both Ga³⁺ and Al³⁺ can be extracted in the form of a neutral complex, MA₃, but the distribution coefficient of Ga³⁺ is the higher by about two orders of magnitude, which can be the basis of the solvent extraction separation of gallium and aluminium. The differences can be explained by the interaction between the sulphur donor atoms of the extractants and the d¹⁰ electronic shell of Ga³⁺ as well as by the lower steric hindrance of ligands co-ordinated to Ga³⁺.     

Speciation of Se,Fe and Zn in Human Milk Whey: The use of Instrumental Neutron Activation Analysis (INAA) to corroborate element profiles measured with Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES)

In human milk trace elements normally exist in a form which can easily be absorbed by the newborn infant. For investigations of the bioavailability of trace elements it is necessary to carry out a speciation analysis of the elements of interest. An independent analytical method has been used for the quality control of the shape of the element profiles obtained from the speciation analysis of Se, Fe and Zn in individual samples of human milk whey after chromatographic separation. For the element detection in the untreated milk fractions Instrumental Neutron Activation Analysis (INAA) was chosen as the reference method. Element distribution patterns have been obtained with Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES) using on-line digestion of the fraction, reduction and hydride formation of Se ("T"-mode). Prior results are compared with those obtained by means of element detection in the untreated fractions ("U"-mode) with ICP-AES. The elution profiles of Se, Fe and Zn in human milk whey obtained by means of ICP-AES detection using the "T"-mode show good agreement with the distribution patterns obtained with INAA. Recoveries of 103% for Fe, 86% for Zn and 87% for Se were obtained. The element distribution patterns of Fe and Zn obtained with ICP-AES speciation using the "T"-mode also show good agreement with those obtained by means of ICP-AES using the "U"-mode.     

The Isocyanide–Cyanide Rearrangement; Mechanism and Preparative Applications

Until recently the isocyanide–cyanide rearrangement was of interest almost solely as an example of a unimolecular gas-phase reaction, and kinetic studies had been carried out in only a few simple cases. Kinetic measurements in solution were made possible only by the discovery and suppression of a parallel free-radical chain process which leads to the same products. The rate of the isomerization is almost independent of the structure of the starting material and of the substituents present. An exception is provided by extreme steric hindrance in three dimensions which, as in tris-α-substituted triptycyl isocyanides, leads to a considerable increase in the activation energy. The results can be interpreted in terms of a purely sigmatropic mechanism, as predicted by ab initio calculations. The preparative application of this rearrangement reaction requires the suppression of side reactions and can best be carried out by flash pyrolysis; yields are then almost quantitative. Allyl isocyanides react without allyl isomerization, optically active isocyanides with complete retention of configuration. New, economically interesting syntheses for the known nonsteroidal anti-inflammatory drugs ibuprofen and (S)-naproxene are described. The application of the useful synthetic building blocks, the optically active β-acyloxy cyanides, which are formed from optically active α-amino acids, will be demonstrated.